Electrical switches are components that either make or break an electrical circuit. Such switches may either interrupt current flow to a conductor, initiate current flow to a conductor, or may divert current flow from one conductor to another.
Switches may take many different forms; the simplest switch is a manually operated electromechanical switch, in which one or more sets of electrical contacts are connected to electrical circuits external to the switch. Each set of contacts can be “open”, meaning the contacts are electrically unconnected, or the contacts may be “closed” meaning that the contacts are electrically connected such that a current flows between the contacts.
A switch may be actuated (meaning that it may change its state) by a human or by various other control means (such as by a sensor signal linked to variables such as temperature, pressure, time, date, current, voltage, force, etc. A switch that is operated by another electrical signal is called a relay.
In the simplest form a switch comprises two or more conductive elements called contacts, each connected to an external circuit in a manner such that when the contacts are made to “touch” they complete (close) the circuit, and when they separate they open (break) the circuit. Contact materials are generally chosen on the basis of their conductivity, hardness, strength, and their resistance to rust, oxidation, and other corrosion.
Switches in which the contacts remain in one state until the switch is actuated (such as a push-button switch) the contacts can either be “normally open” (“NO”) unless closed by the operation of the switch, or “normally closed” (“NC”) unless opened by the actuation of the switch. A switch may have both kinds of contact, in which case it is called a “changeover” switch. A switch can momentarily make the new contact before breaking the contact with the old circuit (“make-before-break” switch or “MBB”) or can break the old circuit before it makes the new one (“break-before-make” switch or “BBM”).
When a switch is designed to switch significant power, the transitional state of the switch as well as the ability to withstand continuous operating currents must be considered. When a switch is in the “on” state, its resistance is near zero and very little power is dropped in the contacts; when a switch is in the “off” state, its resistance is extremely high and even less power is dropped in the contacts. However, when the switch is flicked, the resistance must pass through a state where a significant amount of power (perhaps a quarter of the load's rated power may briefly be dropped in the switch.
For this reason, power switches intended to interrupt a load current often have spring mechanisms to make sure the transition between on and off is as short as possible regardless of the speed at which the user actuates the switch. Thus, for example, a push button power switch may have a spring mechanism wherein initially pushing the button results in an increasing mechanical resistance until a contact is made, at which point continuing to depress the button results in the spring causing the contacts to open again.
Power switches usually come in two types. A momentary on-off switch (such as on a laser pointer) usually takes the form of a button and only closes the circuit when the button is depressed. A regular on-off switch (such as on a flashlight) has a constant on-off feature. In the present invention, preferably the switch, which may be a push button power switch, may have a spring mechanism wherein initially pushing the button results in an increasing mechanical resistance until a contact is made, at which point continuing to depress the button results in the spring causing the contacts to open again.
Pushbutton switches are just one type of commonly used electromechanical switch; other switch types may include rocker switches, toggle switches, sliding switches, rotary switches, float switches, mercury tilt switches, knife switches, and the like.